CNN  —  Many would-be travelers go online to plan their vacations, whether that means looking for the best flight deals and hotel recommendations or more nitty-gritty info about whether their destination of choice requires a visa. In the United States, those preparing for an international trip can check out the State Department’s website for up-to-date info about other countries, which are ranked from “Level 1: Exercise Normal Precautions” to “Level 4: Do Not Travel.” These rankings can change